We are renovating our apartment, and our 2 GCs have been really great. In addition to the two guys who run the GC firm, there are also a ton of other workers: plumbers and their assistants, electrician and his assistant, etc. Since our GCs have been particularly great and helpful, we thought it might be appropriate to give them a card with some extra cash or a gift of some kind for the holidays. In addition, a bunch of the other workers have been doing a lot, and maybe it would be nice to bring something for them, maybe something edible? We have no idea what the conventions might be - anyone have any ideas about what might be standard, or advice about what the contractors would actually most appreciate?

Thanks in advance for any help!